The present invention relates to a disk brake apparatus configured to apply a braking force to a vehicle such as an automobile.
A disk brake is known as a brake apparatus mounted on a vehicle such as an automobile. This disk brake supplies a hydraulic pressure from the outside into a cylinder of a caliper to push a piston toward a surface side of a disk together with brake pads, thereby generating a braking force.
As this disk brake, there is known a hydraulic disk brake provided with an electric parking brake, which is configured to not only generate a braking force based on the hydraulic pressure when the vehicle is running, but also generate a braking force based on driving (a rotation) of an electric motor, for example, when the vehicle is stopped or parked (operate as a parking brake), as discussed in, for example, Japanese Patent Public Disclosure No. 2003-83373.
According to a conventional technique, the disk brake provided with the electric parking brake is configured to thrust the piston toward the disk by driving the electric motor when applying a braking force as the parking brake, and stop driving the electric motor when a current value of the electric motor exceeds a preset threshold value.
A possible method for releasing the parking brake is to stop driving the electric motor according to the current value of the electric motor. However, according to the above-described configuration, the electric motor may excessively rotate depending on how much the hydraulic pressure is at that time, causing a member pushing the piston to be retracted far away from the disk. This results in an increase in a movement amount of the member pushing the piston next time the parking brake is activated, leading to a possibility of deterioration of responsiveness (an increase in a time taken to complete activation of the parking brake).